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The title compound, C
16H
9NO
4, also known as the 3-benzoylpyridinium betaine of squaric acid, exhibits a dipolar electronic ground-state structure with a positively charged pyridinium fragment and a negatively charged squarate moiety. In the molecule, the two aromatic rings are twisted by 56.03 (2)° relative to one another. The three-dimensional packing of the molecules is stabilized by C-H
O short contacts.
Supporting information
CCDC reference: 269033
The synthesis of (I) is described in our previous article (Kolev, Yancheva & Stoyanov, 2004). The crystals were grown by slow evaporation from an acetonitrile solution over a period of a week. Spectroscopic analysis: IR (KBr pellet, ν, cm−1). The νC—H vibrations of the pyridyl ring and benzoyl group appear at 3138 (w), 3130 (w), 3122 (w) and 3107 (w), and at 3092 (w) and 3033 (w), respectively. The very strong band at 1783 (s) is assigned to νC═O of the isolated carbonyl group of the squaric acid ring, while those at 1748 (s) and 1625 (s) correspond to the symmetric and asymmetric modes of the semicarbonyl groups. The pyridinium ring vibration 8a lies in the massive Not clear of the broad band at 1625 (s).
H atoms were placed in idealized positions (C—H = 0.93 Å) and constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C).
Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
2-(3-Benzoyl-1-pyridinio)-3,4-dioxocyclobutenolate
top
Crystal data top
C16H9NO4 | F(000) = 576 |
Mr = 279.24 | Dx = 1.459 Mg m−3 |
Monoclinic, P21/n | Melting point: 418 K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
a = 7.9319 (11) Å | Cell parameters from 22 reflections |
b = 13.6577 (14) Å | θ = 18.4–19.6° |
c = 12.0890 (12) Å | µ = 0.11 mm−1 |
β = 103.903 (12)° | T = 290 K |
V = 1271.3 (3) Å3 | Cubic, red |
Z = 4 | 0.24 × 0.24 × 0.24 mm |
Data collection top
Enraf-Nonius CAD-4 diffractometer | θmax = 28.0°, θmin = 2.3° |
Radiation source: fine-focus sealed tube | h = 0→10 |
non–profiled ω/2θ scans | k = −18→18 |
6407 measured reflections | l = −15→15 |
3063 independent reflections | 3 standard reflections every 120 min |
1558 reflections with I > 2σ(I) | intensity decay: none |
Rint = 0.093 | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.067 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.236 | H-atom parameters constrained |
S = 1.04 | w = 1/[σ2(Fo2) + (0.1235P)2] where P = (Fo2 + 2Fc2)/3 |
3063 reflections | (Δ/σ)max < 0.001 |
190 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.34 e Å−3 |
Crystal data top
C16H9NO4 | V = 1271.3 (3) Å3 |
Mr = 279.24 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 7.9319 (11) Å | µ = 0.11 mm−1 |
b = 13.6577 (14) Å | T = 290 K |
c = 12.0890 (12) Å | 0.24 × 0.24 × 0.24 mm |
β = 103.903 (12)° | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.093 |
6407 measured reflections | 3 standard reflections every 120 min |
3063 independent reflections | intensity decay: none |
1558 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.067 | 0 restraints |
wR(F2) = 0.236 | H-atom parameters constrained |
S = 1.04 | Δρmax = 0.29 e Å−3 |
3063 reflections | Δρmin = −0.34 e Å−3 |
190 parameters | |
Special details top
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
C1 | −0.1537 (4) | 0.2684 (2) | 0.7565 (3) | 0.0501 (8) | |
H1 | −0.2144 | 0.2439 | 0.6865 | 0.060* | |
C2 | −0.0726 (4) | 0.3590 (2) | 0.7617 (2) | 0.0450 (7) | |
C3 | 0.0186 (4) | 0.3943 (2) | 0.8674 (3) | 0.0557 (9) | |
H3 | 0.0744 | 0.4545 | 0.8722 | 0.067* | |
C4 | 0.0264 (5) | 0.3403 (3) | 0.9648 (3) | 0.0645 (10) | |
H4 | 0.0866 | 0.3645 | 1.0351 | 0.077* | |
C5 | −0.0545 (5) | 0.2507 (3) | 0.9586 (3) | 0.0644 (10) | |
H5 | −0.0484 | 0.2144 | 1.0244 | 0.077* | |
C6 | −0.1450 (5) | 0.2147 (3) | 0.8541 (3) | 0.0597 (9) | |
H6 | −0.1999 | 0.1541 | 0.8498 | 0.072* | |
C7 | −0.0922 (4) | 0.4227 (2) | 0.6605 (2) | 0.0498 (8) | |
C8 | −0.1268 (4) | 0.3790 (2) | 0.5435 (2) | 0.0468 (7) | |
C9 | −0.2293 (4) | 0.4294 (2) | 0.4507 (3) | 0.0575 (9) | |
H9 | −0.2784 | 0.4892 | 0.4625 | 0.069* | |
C10 | −0.2581 (5) | 0.3926 (3) | 0.3436 (3) | 0.0642 (10) | |
H10 | −0.3294 | 0.4260 | 0.2830 | 0.077* | |
C11 | −0.1815 (4) | 0.3056 (3) | 0.3247 (3) | 0.0571 (9) | |
H11 | −0.1985 | 0.2805 | 0.2513 | 0.069* | |
C12 | −0.0538 (4) | 0.2919 (2) | 0.5224 (2) | 0.0457 (7) | |
H12 | 0.0149 | 0.2567 | 0.5824 | 0.055* | |
C13 | −0.0073 (4) | 0.1671 (2) | 0.3952 (2) | 0.0482 (8) | |
C14 | −0.0232 (5) | 0.1106 (2) | 0.2940 (3) | 0.0552 (9) | |
C15 | 0.0966 (4) | 0.0350 (3) | 0.3663 (3) | 0.0523 (8) | |
C16 | 0.1077 (4) | 0.1018 (2) | 0.4696 (2) | 0.0470 (7) | |
N1 | −0.0810 (3) | 0.25700 (17) | 0.41463 (19) | 0.0455 (6) | |
O1 | −0.0839 (4) | 0.51134 (16) | 0.6689 (2) | 0.0685 (7) | |
O2 | 0.1785 (3) | 0.09874 (17) | 0.57090 (18) | 0.0602 (7) | |
O3 | −0.1006 (4) | 0.11820 (18) | 0.19422 (19) | 0.0845 (10) | |
O4 | 0.1552 (4) | −0.04321 (19) | 0.3487 (2) | 0.0762 (8) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0590 (19) | 0.0438 (17) | 0.0464 (16) | −0.0001 (15) | 0.0107 (14) | −0.0049 (13) |
C2 | 0.0474 (17) | 0.0409 (16) | 0.0453 (16) | 0.0086 (14) | 0.0086 (13) | −0.0047 (12) |
C3 | 0.0571 (19) | 0.0496 (19) | 0.0543 (19) | 0.0082 (16) | 0.0013 (15) | −0.0119 (15) |
C4 | 0.076 (2) | 0.072 (3) | 0.0417 (18) | 0.018 (2) | 0.0056 (16) | −0.0080 (16) |
C5 | 0.078 (3) | 0.067 (3) | 0.0506 (19) | 0.025 (2) | 0.0200 (17) | 0.0080 (16) |
C6 | 0.077 (2) | 0.050 (2) | 0.058 (2) | 0.0038 (17) | 0.0270 (17) | 0.0033 (15) |
C7 | 0.0578 (19) | 0.0409 (18) | 0.0494 (18) | 0.0007 (15) | 0.0103 (15) | −0.0030 (13) |
C8 | 0.0516 (18) | 0.0416 (17) | 0.0454 (17) | −0.0036 (14) | 0.0082 (13) | 0.0063 (12) |
C9 | 0.064 (2) | 0.0438 (18) | 0.062 (2) | 0.0027 (16) | 0.0085 (17) | 0.0119 (15) |
C10 | 0.074 (2) | 0.060 (2) | 0.049 (2) | −0.0025 (19) | −0.0045 (17) | 0.0178 (16) |
C11 | 0.066 (2) | 0.057 (2) | 0.0398 (16) | −0.0110 (17) | −0.0037 (14) | 0.0104 (14) |
C12 | 0.0525 (18) | 0.0461 (17) | 0.0356 (15) | −0.0026 (14) | 0.0046 (12) | 0.0060 (12) |
C13 | 0.066 (2) | 0.0427 (17) | 0.0334 (14) | −0.0112 (15) | 0.0070 (13) | −0.0012 (11) |
C14 | 0.080 (2) | 0.0471 (18) | 0.0397 (16) | −0.0191 (17) | 0.0161 (15) | −0.0039 (13) |
C15 | 0.058 (2) | 0.0520 (19) | 0.0512 (17) | −0.0142 (16) | 0.0222 (15) | −0.0093 (14) |
C16 | 0.0584 (19) | 0.0448 (17) | 0.0375 (15) | −0.0105 (15) | 0.0110 (13) | −0.0021 (12) |
N1 | 0.0550 (15) | 0.0427 (14) | 0.0350 (12) | −0.0094 (12) | 0.0032 (10) | 0.0042 (10) |
O1 | 0.0944 (19) | 0.0363 (13) | 0.0738 (16) | 0.0009 (12) | 0.0178 (14) | −0.0027 (10) |
O2 | 0.0718 (15) | 0.0600 (15) | 0.0436 (13) | 0.0066 (12) | 0.0038 (11) | 0.0000 (10) |
O3 | 0.147 (3) | 0.0612 (16) | 0.0353 (13) | −0.0209 (16) | 0.0015 (14) | −0.0074 (10) |
O4 | 0.0841 (19) | 0.0626 (17) | 0.0831 (19) | 0.0035 (14) | 0.0225 (14) | −0.0252 (14) |
Geometric parameters (Å, º) top
C1—C6 | 1.377 (4) | C9—C10 | 1.356 (5) |
C1—C2 | 1.389 (4) | C9—H9 | 0.9300 |
C1—H1 | 0.9300 | C10—C11 | 1.378 (5) |
C2—C3 | 1.394 (4) | C10—H10 | 0.9300 |
C2—C7 | 1.478 (4) | C11—N1 | 1.357 (4) |
C3—C4 | 1.379 (5) | C11—H11 | 0.9300 |
C3—H3 | 0.9300 | C12—N1 | 1.355 (4) |
C4—C5 | 1.374 (5) | C12—H12 | 0.9300 |
C4—H4 | 0.9300 | C13—N1 | 1.404 (4) |
C5—C6 | 1.385 (5) | C13—C14 | 1.426 (4) |
C5—H5 | 0.9300 | C13—C16 | 1.430 (4) |
C6—H6 | 0.9300 | C14—O3 | 1.220 (4) |
C7—O1 | 1.216 (4) | C14—C15 | 1.527 (5) |
C7—C8 | 1.498 (4) | C15—O4 | 1.204 (4) |
C8—C12 | 1.374 (4) | C15—C16 | 1.533 (4) |
C8—C9 | 1.398 (4) | C16—O2 | 1.219 (3) |
| | | |
C6—C1—C2 | 120.6 (3) | C9—C10—C11 | 119.8 (3) |
C6—C1—H1 | 119.7 | C9—C10—H10 | 120.1 |
C2—C1—H1 | 119.7 | C11—C10—H10 | 120.1 |
C3—C2—C1 | 118.8 (3) | N1—C11—C10 | 119.1 (3) |
C3—C2—C7 | 118.9 (3) | N1—C11—H11 | 120.4 |
C1—C2—C7 | 122.0 (3) | C10—C11—H11 | 120.4 |
C4—C3—C2 | 120.3 (3) | N1—C12—C8 | 120.4 (3) |
C4—C3—H3 | 119.8 | N1—C12—H12 | 119.8 |
C2—C3—H3 | 119.8 | C8—C12—H12 | 119.8 |
C5—C4—C3 | 120.3 (3) | N1—C13—C14 | 131.5 (3) |
C5—C4—H4 | 119.9 | N1—C13—C16 | 132.0 (2) |
C3—C4—H4 | 119.9 | C14—C13—C16 | 96.5 (3) |
C6—C5—C4 | 120.0 (3) | N1—C13—C15 | 179.1 (3) |
C6—C5—H5 | 120.0 | O3—C14—C13 | 136.2 (3) |
C4—C5—H5 | 120.0 | O3—C14—C15 | 136.0 (3) |
C5—C6—C1 | 120.0 (3) | C13—C14—C15 | 87.8 (2) |
C5—C6—H6 | 120.0 | O4—C15—C14 | 135.4 (3) |
C1—C6—H6 | 120.0 | O4—C15—C16 | 136.3 (3) |
O1—C7—C2 | 121.6 (3) | C14—C15—C16 | 88.2 (2) |
O1—C7—C8 | 118.0 (3) | O4—C15—C13 | 179.1 (3) |
C2—C7—C8 | 120.4 (3) | O2—C16—C13 | 136.4 (3) |
C12—C8—C9 | 117.8 (3) | O2—C16—C15 | 136.1 (3) |
C12—C8—C7 | 122.0 (3) | C13—C16—C15 | 87.4 (2) |
C9—C8—C7 | 120.1 (3) | C12—N1—C11 | 121.7 (3) |
C10—C9—C8 | 121.1 (3) | C12—N1—C13 | 119.5 (2) |
C10—C9—H9 | 119.5 | C11—N1—C13 | 118.8 (3) |
C8—C9—H9 | 119.5 | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H9···O3i | 0.93 | 2.59 | 3.225 (4) | 125 |
C10—H10···O2ii | 0.93 | 2.60 | 3.215 (3) | 124 |
C11—H11···O3 | 0.93 | 2.50 | 3.152 (5) | 127 |
C12—H12···O2 | 0.93 | 2.54 | 3.191 (4) | 127 |
Symmetry codes: (i) −x−1/2, y+1/2, −z+1/2; (ii) x−1/2, −y+1/2, z−1/2. |
Experimental details
Crystal data |
Chemical formula | C16H9NO4 |
Mr | 279.24 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 290 |
a, b, c (Å) | 7.9319 (11), 13.6577 (14), 12.0890 (12) |
β (°) | 103.903 (12) |
V (Å3) | 1271.3 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.24 × 0.24 × 0.24 |
|
Data collection |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6407, 3063, 1558 |
Rint | 0.093 |
(sin θ/λ)max (Å−1) | 0.660 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.067, 0.236, 1.04 |
No. of reflections | 3063 |
No. of parameters | 190 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.34 |
Selected bond lengths (Å) topC2—C7 | 1.478 (4) | C14—O3 | 1.220 (4) |
C7—O1 | 1.216 (4) | C14—C15 | 1.527 (5) |
C7—C8 | 1.498 (4) | C15—O4 | 1.204 (4) |
C13—C14 | 1.426 (4) | C15—C16 | 1.533 (4) |
C13—C16 | 1.430 (4) | C16—O2 | 1.219 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H9···O3i | 0.93 | 2.59 | 3.225 (4) | 125 |
C10—H10···O2ii | 0.93 | 2.60 | 3.215 (3) | 124 |
C11—H11···O3 | 0.93 | 2.50 | 3.152 (5) | 127 |
C12—H12···O2 | 0.93 | 2.54 | 3.191 (4) | 127 |
Symmetry codes: (i) −x−1/2, y+1/2, −z+1/2; (ii) x−1/2, −y+1/2, z−1/2. |
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The substituted pyridinium betaines of squaric acid are of particular interest as potential organic nonlinear optical (NLO) materials (Chemla & Zyss, 1987; Nalwa et al., 1997; Wolff & Wortmann, 1999). In the course of our detailed study of squaric acid derivatives, the syntheses and structural characterizations of the 4-benzoyl (Kolev et al., 2001), 4-dimethylamino (Kolev, Yancheva et al., 2002) and 4-methoxy analogues (Kolev, Wortmann et al., 2004) have been published. In view of the very interesting chemical structure of this type of molecules, density functional theory calculations of the electronic structure and UV–vis spectroscopic studies have been carried out (Kolev et al., 2003; Kolev, Stamboliyska et al., 2004; Kolev, Yancheva & Stoyanov, 2004). The electro-optical absorption measurements (EOAM) demonstrate that the studied series of compounds possess hyperpolarizabilities exceeding that of the reference substance, p-nitroaniline, both in absolute and relative values. These results are due to be published shortly. In this paper, we report the structural characteristics of the 3-benzoylpyridinium-betaine of squaric acid, (I).
The molecular structure of (I) is dipolar, with the positive and the negative charges situated on the pyridinium and squarate groups, respectively (Fig. 1). One of the C—O bonds within the squarate system has a value of 1.204 (4) Å, typical for carbonyl group. The remaining two C—O bonds are longer and have similar values [1.219 (3) and 1.220 (4) Å], indicating that the negative charge is equally distributed between atoms O2 and O3. This charge repartition also affects the cyclobutene C—C distances, with two of them being shorter than the other two, with respective values of 1.426 (4)–1.430 (4) and 1.527 (5)–1.533 (4) Å. A similar deformation of the squarate moiety is known for the 4-benzoyl derivative (Kolev et al., 2001). The squarate and pyridinium rings are nearly coplanar, with a dihedral angle of 4.1 (2)°. A similar value of this angle was observed in previously described structures of this type. The dihedral angle between the aromatic rings is 56.0 (1)° [56.03 (2)° in Abstract?]. This is comparable with the corresponding value in 4-dimethylamino-4'-nitrobenzophenone (Kolev, Schurmann et al., 2002) and differs significantly from that in the 4-benzoyl derivative (Kolev et al., 2001), where the aromatic rings are nearly perpendicular.
The molecule of (I) is Λ shaped, i.e. the rings are mutually twisted (Nalwa et al., 1997). In the crystal, the molecules face each other in an alternate end-to-end fashion, so that opposite shoulders of the molecules are adjacent to each other. There are a number of intermolecular interactions stabilizing the three-dimensional packing of the molecules. We consider two of them as non-classical hydrogen bonds, namely the contacts between the negatively charged squarate O atoms and the pyridinium H atoms (Table 1). These contacts are likely to occur due to the greater mobility of H atoms within the pyridinium ring, caused by the electron-withdrawing N atom. A similar manner of hydrogen bonding is known in the previously reported 4-benzoyl analogue, where the molecules are linked to form ribbons. In contrast, the molecules of the title compound are two-dimensionally connected (Fig. 2).
It is interesting to note that the coplanarity between squarate and pyridinium rings determine two additional short contacts C11···O3 and C12···O2 which could be explained as intramolecular hydrogen bonds. Similar short contacts are found in the 4-benzoyl analog.